Numerical Simulation Of Pulsating Flow And Heat Transfer In Tubes

Pulsating flow and heat transfer phenomenon exists widely in industrial fields, such as metallurgy, aviation, chemical and food industry. It is generally recognized that pulsating flow can enhance heat transfer rate. Although researchers have presented many researches, the results they have gained are not always consistent and some of them are even incompatible. The reason is that the heat transfer process in pulsating flow is so complicated. However, pulsating flow and heat transfer can not be neglected in practical projects.The simulation for laminar pulsating flow and heat transfer in tube is presented first. Then the simulation for turbulent pulsating flow and heat transfer is done with standard turbulent model and experimental parameters which comes from the tail tube of a pulsating burner. The Von Karman constant is modified in order to suit for the experiment condition, and turbulent pulsating model is established. The influence of amplitude and frequency on turbulent flow and heat transfer is studied. The main conclusion obtained as follows:(1) Laminar pulsating flow with the periodical variation velocity as the entrance boundary condition of the tube is investigated. The results shows that the velocity, temperature, pressure are not changed with time in stable state; while in pulsating flow, the velocity, pressure and surface friction coefficient are fluctuated around the stable values at the same Reynolds number . The velocity margin of fluctuation has the inverse ratio with frequency. The moment trend of surface friction coefficient and pressure is in direct proportion to velocity amplitude and frequency. From the analyzing of velocity distribution, the back flow comes out near the inner surface, and the time of duration for back flow increases along with the growing of the frequency and amplitude. Re(2) The experimental data of gas in the tail tube of the pulse combustor are compared with the simulation results, concluding that the Von Karman constant value is 0.48~0.52 under the experimental condition.(3) Taking the periodic variation pressure as the entrance boundary condition, turbulent pulsating flow and heat transfer is researched, and the value of the Von Karman constant is 0.5. The velocity distribution is similar to the ellipse distribution in the full development turbulent flow. The velocity variation at the instant pulsating flow section is smooth in most of the channel. The velocity varies significantly near the inner surface and it gets the peak value here. The distribution of temperature and velocity present the periodical variation. The larger of pressure amplitude, the wider variation range of fluctuation. It will inverse for frequency. The wall surface friction coefficient declines when the pressure amplitude rises, and it increases when the frequency increases. The surface heat transfer coefficient increases along with the growing of the pressure amplitude and declines with the growing of frequency.